Beyond the first wave: understanding binary neutron star and black hole formation channels

Abstract: After the first waves of gravitational-wave detections, it often seems as though we are left with more questions than answers. The hope of finding “one formation channel to rule them all” has given way to “one channel for every system.” This shift is not necessarily a drawback: moving away from a single unifying framework allows us to focus on specific properties—such as mass ranges—and connect observed features to their progenitors. In this talk, I will focus on lower-mass compact objects and discuss key findings on which recent studies are converging, such as: why binary neutron stars are expected to form through only a single channel, and why binary black hole formation is metallicity dependent, while binary neutron star formation is not (or much less so). I will explore the “if” and “why” behind each of these findings, their broader implications for merger predictions and cosmology, and how we can test them with upcoming gravitational-wave and electromagnetic observations.